The invention relates to a microstructured arrangement for the bubble-free filling with a liquid of at least one system for draining off liquids (liquid-discharging system). The invention also relates to an apparatus having such an arrangement and a method for filling a system for draining off liquids having such an arrangement.
During transport of liquids on the basis of capillary forces in microstructure systems, there are problems over and over again with air bubbles in the transport paths. These can inhibit or even prevent the desired liquid transport. Air bubbles are often formed when the liquid stream is deflected, for example when the channel changes direction through 90°. The edges present in the corner region lead to this corner region not being fully wetted by the liquid and liquid penetrating into the channel section bent over through 90° (liquid-discharging system) before the corner region is fully wetted by the liquid. The liquid stream then flows past the air bubble formed in the corner region and penetrates into the 90°-angled section of the channel. However, the air bubble in the corner region can become detached from the corner region in the further course of time and settle as a plug upstream of the channel section angled over through 90°, that is to say the liquid-discharging system. Further liquid transport can be prevented or at least hampered thereby.
Similar effects can occur when liquids are to be led via a branching point into various liquid-discharging systems. Here, too, it is not necessarily ensured that the branching point is filled completely with liquid and no air bubbles are contained at the branching point before all the liquid-discharging systems are wetted and filled with liquid.
The document bearing the publication number EP 1 201 304 A2 discloses a microstructure platform for the examination of liquid in which various cavities are filled with liquids by means of capillary forces. For example, FIG. 4 of the document discloses a chamber 130 which is filled via a feed channel 450. The chamber has a comparatively great depth and the feed channel opens immediately below the cover of the chamber, the opening region having a small cross-sectional area and, therefore, there being in the opening region an abrupt transition from the small cross-sectional area of the feed channel to the large cross-sectional area of the chamber, which acts as a capillary stop, at which liquid transport breaks down. However, in order not to have the liquid transport break down and to permit the chamber to be fed at all via the feed channel, a notch 440 is provided which extends from the opening region of the feed channel as far as the bottom of the chamber, in the side wall of the chamber. In the notch there is an increased capillary force, which has the effect that liquid brought up by the feed channel is drawn along the notch to the bottom of the chamber. The notch leads the liquid to the bottom of the chamber in this way and, from the bottom of the chamber, the liquid then rises into the chamber. Before the chamber is filled completely with the liquid, the outlet of the chamber is wetted toward the inlet structure 410 and liquid emerges from the chamber 130. However, air is then enclosed in the chamber 130, which is undesired.
The document WO 99/46045, FIGS. 4 and 5, discloses a similar notch, designated an inlet channel 62 there, which fulfills the same purpose as the notch in the document EP 1 201 304 A2.
In addition, in the document EP 1 201 304 A2, cascade and butterfly structures are described which permit uniform propagation of a liquid stream into a liquid layer flowing at a uniform speed (or, conversely, uniform combination of a broad liquid stream). These cascade and butterfly structures on their own do not ensure the bubble-free filling of an adjacent chamber, however. Instead, the chamber itself must have delay structures at the edges, which prevent an edge flow running ahead and thus the entrainment of air bubbles.
The invention is based on the object of proposing an arrangement and an apparatus having such an arrangement, and also a method for operating such an arrangement, which ensure that the liquid-discharging system or systems are filled without any bubbles.